The drought that has the entire country in its grip is affecting more than the color of people’s lawns. It may also be responsible for the proliferation of a heat-loving amoeba commonly found in warm freshwater bodies, such as lakes, rivers and hot springs, which the drought has made warmer than usual this year.

A 9-year-old Kansas girl recently died of an infection caused by this parasite after swimming in several area lakes. The amoeba enters the body through the nose of an individual and travels to the brain. Nose plugs can lower the odds of this rare but fatal pathogen entering the body.

The amoeba, Naegleria fowleri, is classified as a sapronosis, an infectious disease caused by pathogenic microorganisms that inhabit aquatic ecosystems and/or soil rather than a living host. Scientists at UC Santa Barbara studying infectious disease transmission published their findings in the latest issue of the journal Trends in Parasitology.

“Sapronoses do not follow the rules of infectious diseases that are transmitted from host to host,” said lead author Armand Kuris, a professor in UCSB’s Department of Ecology, Evolution and Marine Biology. “They are categorically distinct from the way we think infectious diseases should operate. The paper tries to bring this group of diseases into sharp focus and get people to think more clearly about them.”

A well-known example of a sapronosis is Legionnaires’ disease, caused by the bacteria Legionella pneumophila, which can be transmitted by aerosolized water and/or contaminated soil. The bacteria can even live in windshield-wiper fluid. Legionnaires’ disease acquired its name in July 1976, when an outbreak of pneumonia occurred among people attending an American Legion convention at the Bellevue-Stratford Hotel in Philadelphia. Of the 182 reported cases, mostly men, 29 died.

A major group of emerging diseases, sapronotic pathogens can exist independently in an environmental reservoir like the cooling tower of the Philadelphia hotel’s air conditioning system. Some, like the cholera protozoa, rely on mosquitoes to find disease hosts for them. Zoonoses, by contrast, require a human host.

According to Kuris, diseases borne by a vector — a person, animal or microorganism that carries and transmits an infectious pathogen into another living organism — are more or less virulent depending on how efficiently they are transmitted. As a result, virulence evolves to a level where it is balanced with transmission in order to maximize the spread of the virus. However, Kuris noted that there is no virulence trade-off for sapronotic disease agents. Transmission of a sapronosis pathogen is able to persist regardless of any changes in host abundance or transmission rates.

To quantify the differences between sapronoses and conventional infectious diseases, the researchers developed a mathematical model using population growth rates. Of the 150 randomly selected human pathogens examined in this research, one-third turned out to be sapronotic — specifically 28.6 percent of the bacteria, 96.8 percent of the fungi and 12.5 percent of the protozoa.

“The fact that almost all of the fungi we looked at are sapronotic is a noteworthy generalization,” Kuris said.

“You can’t model a sapronosis like valley fever with classic models for infectious diseases,” said co-author Kevin Lafferty, adjunct faculty in EEMB and a marine ecologist with the Western Ecological Research Center of the U.S. Geological Survey. “To combat sapronoses, we need new theories and approaches. Our paper is a start in that direction.”

Support Noozhawk Today

You are an important ally in our mission to deliver clear, objective, high-quality professional news reporting for Santa Barbara, Goleta and the rest of Santa Barbara County. Join the Hawks Club today to help keep Noozhawk soaring.

We offer four membership levels: $5 a month, $10 a month, $25 a month or $1 a week. Payments can be made using a credit card, Apple Pay or Google Pay, or click here for information on recurring credit-card payments and a mailing address for checks.

Thank you for your vital support.

Become a Noozhawk Supporter

First name

Last name

Email

Select your monthly membership

Red-Tailed Hawk $5/month

Cooper's Hawk $10/month

Red-Shouldered Hawk $25/month

Or choose an annual membership

Birds of a Feather $52/year

×

Payment Information

Membership Subscription

You are enrolling in . Thank you for joining the Hawks Club.

Payment Method

Pay by Credit Card:

Credit or debit card

Mastercard, Visa, American Express, Discover

One click only, please!

Pay with Apple Pay or Google Pay:

Noozhawk partners with Stripe to provide secure invoicing and payments processing.
You may cancel your membership at any time by sending an email to .(JavaScript must be enabled to view this email address).

Welcome to Noozhawk Asks, a new feature in which you ask the questions, you help decide what Noozhawk investigates, and you work with us to find the answers.

Here’s how it works: You share your questions with us in the nearby box. In some cases, we may work with you to find the answers. In others, we may ask you to vote on your top choices to help us narrow the scope. And we’ll be regularly asking you for your feedback on a specific issue or topic.

We also expect to work together with the reader who asked the winning questions to find the answer together. Noozhawk’s objective is to come at questions from a place of curiosity and openness, and we believe a transparent collaboration is the key to achieve it.

The results of our investigation will be published here in this Noozhawk Asks section. Once or twice a month, we plan to do a review of what was asked and answered.

Reader Comments

Noozhawk is no longer accepting reader comments on our articles. Click here for the announcement. Readers are instead invited to submit letters to the editor by emailing them to [email protected]. Please provide your full name and community, as well as contact information for verification purposes only.